Process and product for removing rust and coating materials



United States Patent 3,097,118 PROCESS PRODUCT FQR REMOVENG RUST ANDCOATHNG MATERHALS Clarence E. Leonard, 204% Martin Road, lit. QlairShores, Mich. No Drawing. Filed Nov. El, 1959, Ser. No. 851,542 3Claims. (Cl. 148-615) My invention relates to a new and usefulimprovement in a process and product for removing and preventing rust,and has for its object the provision of a means for protecting metalsparticularly of the ferrous variety against corrosion and removal ofrust therefrom when formed.

Another object of the invention is the provision of a process wherebythe metal to be treated is immersed in a composition consisting of rustremoving material and rust inhibiting material so that when the metal isremoved from the immersion, it will be free from rust and the rustinhibiting compound will cling to the surface of the metal and serve asa rust inhibiting coating thereon.

Another object of the invention is the provision of a metal treatingcomposition consisting of a mixture of a compound of rust removingmaterial and a compound of rust inhibiting material.

Another object of the invention is the provision of a composition ofthis type in which when the metal is immersed gassing is reduced to aminimum.

Other objects will appear hereinafter.

It will be apparent from the description \given that variations andmodifications may be made from the exact detail of the structureillustrated without departing from the invention, and it is intendedthat the present disclosure shall be considered to be but the preferredembodiment.

The common method of protection of metals of the ferrous variety againstcorrosion involves various steps. The surface must be thoroughly cleanedfrom all oil and grease and all rust must be removed or inactivatedprior to the application of protective coatings such as paints,varnishes, enamels, lacquers, etc. The elfective life of such coatingsis materially reduced when applied over metals which have not beenproperly prepared, particularly where rust and corrosive scale have notbeen removed.

Rust under the present method is usually removed by mechanical orchemical means. Mechanically it may be accomplished by such methods aswire brushing, sand or shot blasting, scraping, the use of abrasivewheels, abrasive paper, steel wool, etc. By chemical methods it iscustomary to apply acids, notably the mineral acids such as phosphoric,sulfuric or hydrochloric, either individually or mixed, and frequentlysalts and/ or other modifying agents are added. The present invention isprimarily concerned with the chemical methods of rust removal, theobjective being the development of simpler and more convenientprocedures, and to extend the processes to include the deposition of animpervious film to provide longer protection of the base metal aftertreating.

Ferrous metals that have been treated with such acids as sulfuric,hydrochloric, nitric, etc., tend to rust again soon after the acid hasspent itself or been rinsed off. There are special rinses to delay thissecondary rusting, such as chromic acid, solutions of chromium trioxide,in conjunction with dilute phosphoric acid. While these 'methods arequite effective in rust removal they do not provide permanent protectionagainst subsequent rusting unless followed by the application of paint,varnish, oil or similar continuous films.

The use of phosphoric acid and phosphates commonly referred to asphosphating differs from most mineral 3,697,118 Patented July 9, 1963acid compounds in that not only is rust removed but simultaneously anadherent film of mineral salts is formed on the metal which extends theperiod of immunity toward rusting, frequently to several months ofinside storage prior to painting. This added protection, however, inmany cases is not sufficient, particularly where there is high humidityor where the treated article must be stored outside, unpainted, for aconsiderable length of time.

The protective cycle provided by phosphating will depend to anappreciable degree upon the composition of the treated metal. And,Whether one of the special rinses will be required is likewisedetermined largely by the type of metal involved.

It is obvious that the decorative processing of ferrous metals in manyinstances is time consuming and expen sive, and any simplification oreconomic improvement without sacrifice of quality is highly desirable.

An immediate approach to such improvement would be the incorporation ofrust removing ingredients to the paint material itself prior toapplication. There are many adverse factors which in the past have madeit quite impossible to mix such components into a useful, homogeneousproduct. Since the primitive advent of protective coatings thepredominating paint materials have been of the organic-solvent type,ordinarily immiscible with water in any appreciable amount. Conversely,the conventional rust removers are water soluble and usually supplied inaqueous solution, and consequently are incompatible with organic solventtype paints. Therefore such a mixture will be either too dilute to serveas a rust remover, or its film forming properties will be deterioratedbelow the range of practical usefulness.

In recent years the water emulsion type of protective finishes has beenprogressively assuming increased popularity, and there is sound reasonfor this transition. They do not contain volatile, flammable organicsolvents, and thus the extremely dangerous fire hazard always associatedwith lacquers, shellac, oil varnishes and paints, is absent. As a resultindustrial insurance rates where paint operations are employed, arematerially lowered. The absence of toxic vapors is particularlyadvantageous from the standpoint of personnel.

Since the organic thinners are volatile, and therefore lost as the paintfilm dries, their use is an expensive medium of application. Thecontrasting merit of using water as thinner stresses the importance anddesirability of extensive exploitation of emulsion paints. While theyoffer many features of excellent superiority, they have one adverseproperty of deep concern. Containing upwards of fifty percent water, andmore, they invariably induce rusting when applied directly to ferrousmetals. If this defect could be corrected the emulsion paints could besuccessfully used on water wet metal, which is quite impossible with theorganic solvent type of finish.

It is, of course, apparent that the above rust removers and emulsionpaints have at least one common factor, namely the aqueous phase. Thiscommon property suggests the feasibility of incorporating the twocompounds into a stable, homogeneous product capable of retaining theindividual characteristics of the two compounds and thus serve as a rustremover-inhibitor, and also have the capacity of depositing a normalpaint film for prolonged protection. In efiect, a paint material wouldbe produced which could be successfully applied over rusted metal, wetor dry, in one operation. It must be observed however, that a search forsuch an optimum combination is confined within definite limitations. Thesimple presence of the common aqueous phase is no assurance that theintroduction of the acidic rust remover will not disrupt the emulsionequilibrium by altering, for example, the hydrogen ion concentration,one of the vital factors upon which that equilibrium sometimes depends.

Among the more prominent representatives of the fixed vehicles employedin paint emulsions are such resinous bodies as the poiyethylenes, thepolyvinyl acetates and chlorides, styrenated butad-ienes, latex, and theacrylics such as methyl methacrylate. Many members of these groups, andothers, were studied in the search for a suitable combination to fulfillthe requirements and many of them fell short in one respect or another.The polyvinyls as a whole gave very good indications and some excellentproducts were formulated with their use. And some members of the othergroups have qualities that Warrant further consideration. However, itwas found that espeoially the polyacrylic acid esters, at the presentstage of development, show some margin of superiority and are beinggiven prior consideration, while concurrently work is continued with theother resins.

The acrylic esters when mixed with phosphoric rust remover have theunique property of accelerating the rate of rust removal, a highlydesirable contribution to the product. It is not unusual for moderaterust to be removed in only two minutes immersion, at room temperature,while ordinarily considerably more time would be required. Gassing isheld at a minimum, which is also a point of superiority.

The combination may be used with or without pigmentati on. In theabsence of pigments or dyes the resulting film is Water white andtransparent. Soluble dyes yield colored transparent films, andpigmented, opaque films have been successfully made in white, red,brown, gray and black, with and without inerts. By orthodox adjustmentof the pigment-fixed vehicle ratio these colors have been produced withlight reflectivity varying from high gloss enamels to conventionalflats.

The actual formula is extremely flexible since the major ingredients arecompatible in all proportions. In practice, the formula Will varybetween Wide limits and is governed by the type of metal beingprocessed, the nature and degree of rust or corrosion, the method ofapplication, and required properties of the final film.

A representative formula of a rust remover, which may be termedcomposition A, is as follows:

Parts by weight A film forming composition which may be referred to ascomposition B? is as follows:

Polyaorylic acid ester water emulsion, 50% total solids In use, the twocomponents, that is compound A and compound B are thoroughly mixedtogether and the metal to be treated is immersed into the mixture soobtained. Compound A will immediately set to work to remove the rustfrom the metal, the larger pieces of rust being deposited in the bottomof the tank or container in which the mixture is deposited, and thesmaller pieces of rust going into solution. As the rust is removed, aphosphating process of the metal begins, which continues for some timeto build a film of phosphates or mineral salts on deposit. This film isporous and does not protect against moisture penetration or subsequentrusting. When the metal is Withdrawn from the tank from which it isimmersed, the metal will be wet with the film forming component whichpenetrates the film. As the water in compound A and the Water ofcompound B evaporate, compound B will form a protective film on themetal to prevent further rust. It is thus seen that the rust inhibitoris deposited immediately upon the removal of rust from the metal so thata substantially indefinite life period of protection is obtained.

The rust treating and film forming components, that is compound A andcompound B are miscible in all proportions. Their ratios can thereforebe adjusted between infinitely wide limits, from a mixture on the oneextreme comprised almost entirely of the rust treating component, to amixture at the other extreme which is almost entirely film former. Thepractical significance of this optional range is apparent, since theapplication requirements will likewise vary widely, betweencorresponding limits. For example, on machine parts where dimensionaltolerances must be held at a minimum, particularly where the machine isoperating in a relatively dry atmosphere, the optimum mixture would bepredominately the rust inhibiting solution, with only a very smallamount of film former. Conversely, where fresh rolled or cast stock isbeing treated, which is already free of rust, the preferred mixturewould be principally the film former, with only enough rust inhibitorpresent to prevent rust formation by the water in the emulsion phase,and at the same time improve adhesion of the final film to the basemetal.

While some of the resin emulsions used as protective film formers havean acid pH, or neutral, the majority of them are alkaline. Conversely,the rust treating compound is obviously aoid. In cross-blendingthroughout the above wide range, therefore, the final mixtures will varyin pH value from strongly acid to alkaline, depending upon thepredominating component. For example, a mixture of 99% solution A, inthe preliminary discussion, and 1% emulsion B, will approximate the highacidity of A itself, while a mixture of 1% A and 99% B will have analkaline pHof upwards of 11. The mixtures at these two extremes, and allintermediate ratios, are stable, where a non-pigmented formulation isemployed, with all of the previously indicated resin emulsions.

Some pigments are reactive toward the relatively high acidity of therust treating compound and consequently when they are introduced intothe system the amount of this component must be reduced to insurecompatibility. In general, with pigmentation, the maximum practicaltolerance of the rust treating component in the mixture is double theamount of resin emulsion used, while the optimum will usually fall belowthis amount. The minimum quantity of solution A is determined by therequirements of any given application, extending down to the low valuesnoted above, namely 1% or less.

Compound A is not confined to the specific formula as shown in thepreliminary discussion. The formula components can be adjusted throughWide ranges and still yield products that will very effectively act asrust remover-inhibitor. And other metal salts can be used as replacementfor, or addition to those shown. This is generally recognized in thefield of rust treatment. The formula shown as A is a good representativeof the field of such compounds, and functions particularly well in themixtures under discussion.

The emulsions in B 55 total solids. desirable.

The following examples illustrate the wide scope of useful combinations:

are usually stocked at 45 to They can be further diluted when Example 1Parts by weight 1 to 100 1 to 100 0 to 100 0 to 15 0 to. 15

1 to 200 60 to 200 0 to 400 0 to 40 The resins in B may be:

Acrylics, such as methyl methacryl-ate. Vinyls, such as vinyl acetate orchloride. Latexes, such as styrene butadiene. Alkyds, etc. Typicalwetting agents are:

Lecithin. Alkali polyphosphates. Sodium di (Z-ethylhexyl)sulfosuccinate. Suitable amti4foaming agents are:

Silicones. Tributyl phosphate. Diethylhexyl ether. Sulfonated castoroil. Representative dispersing agents are:

Sodium lignosulfonate. Polycarboxylic naphthalene sulfonate polymer.Octyl phenol polyoxyethylene. Polyoxyethylene sorbitan monolaurate.Tetrasodium pyrophosphate. Satisfactory inert extenders are:

Barytes. Silica. Asbestine. Bentonite. Pigments are:

Titanium dioxide. Red oxide of iron. Black oxide of iron. Carbon blacketc.

The pigments and inerts may be used individually or cross-blended in themixtures.

In the above examples I have selected those film formers which ingeneral are preferred, and have been extensively used for this purpose.

It will be noted that the preferred compound B which specifies acrylics,in a water emulsion, may be substituted by vinyls, such as vinyl acetateor chloride, latexes, such as styrene butadiene, alkyds, etc.

Anti-foaming agents are used for the obvious purpose.

Experience has shown that the metal when treated in the manner indicatedis rust proofed over an indefinite period of time and that a quick andeconomical operation is obtained.

What I claim is:

1. A composition of matter for coating and protecting metals from rustand for removing rust therefrom consisting essentially of phosphoricacid 1,650 parts by weight, iron phosphate 18 parts by weight, zincchromate 52 parts by weight, manganese sulfate 46 parts by weight andwater 2,763 parts by weight, mixed with polyacrylic acid ester wateremulsion, 50% total solids.

2. A composition of matter for coating and protecting metals from rustand for removing rust therefrom consisting essentially of phosphoricacid 1,650 parts by weight, iron phosphate 18 parts by weight, zincchromate 52 parts by weight, manganese sulfate 46 parts by weight, andwater 2763 parts by weight; mixed with a polyacrylic acid ester Wateremulsion containing 25 to percent total solids.

3. The method of coating and protecting metal from rust and for removingrust therefrom, consisting in sub jecting the metal to the action of acomposition of matter consisting essentially of an aqueous solution offree phosphoric acid, mixed with a polyacrylic acid ester wateremulsion, the amount of said free phosphoric acid in said compositionbeing sufficient to remove rust from said metal and to protect saidmetal from rust, and the amount of said polyacrylic acid ester in saidcomposition being suflicient to form a coating on said metal.

References Cited in the file of this patent UNITED STATES PATENTS2,120,212 Curtin June 7, 1938 2,203,670 Buzzard June 11, 1940 2,224,695Prutton Dec. 10, 1940 2,411,590 Powell Nov. 26, 1946 2,493,327 VanceJan. 3, 1950 2,525,107 Whiting et al. Oct. 10, 1950 2,568,424 WatsonSept. 18, 1951 2,609,308 Gibson Sept. 2, 1952 2,636,257 Ford Apr. 28,1953 2,811,471 Homeyer Oct. 29, 1957 2,816,051 Harford Dec. 10, 1957

1. A COMPOSITION OF MATTER FOR COATING AND PROTECTING METALS FROM RUSTAND FOR REMOVING RUST THEREFROM CONSISTING ESSENTIALLY OF PHOSPHORICACID 1,650 PARTS BY WEIGHT, IRON PHOSPHATE 18 PARTS BY WEIGHT, ZINCCHROMATE 52 PARTS BY WEIGHT, MANGANESE SULFATE 46 PARTS BY WEIGHT ANDWATER 2,763 PARTS BY WEIGHT, MIXED WITH POLYACRYLIC ACID ESTER WATEREMULSION, 50% TOTAL SOLIDS.